Smokers will be stopped in the street and asked to take a carbon monoxide test in London’s most hard-hitting anti-smoking campaign.

‘Smoking police’ will target people at betting shops, bus stops and shopping centres to shock them into giving up cigarettes.

They will be asked to breathe into a monitor to show how much carbon monoxide is in their bodies, and could then be signed up to local stop-smoking services and given access to counsellors.

Pro-smoking group Forest described the campaign as a humiliating infringement of civil liberties.

Ealing Primary Care Trust, which is funding the £75,000 scheme, said it could help 2,400 people to give up.

A team of 11 young people have been employed to approach smokers, in a similar way to charity fund-raisers – nicknamed ‘chuggers’ – who ask passers-by for donations.

Project spokeswoman Fran Pearce admitted: ‘They will have to be careful when approaching smokers in case they become aggressive, but we are interested to see how it pans out. If someone says no, they will not pressure them to take the test.’

Project manager Phil Robinson of Ealing Stop Smoking-Service said: ‘The law to ban smoking in public places was hugely effective, but since then some focus has been lost.

‘We want to put stopping smoking back on the agenda, so 50 per cent of our current activity is about personalising and localising our campaign and taking our message direct to smokers.’

He added: ‘We will be focusing on betting shops, transport stops, walk-throughs, shopping centres and leisure areas where most smoking takes place.’

There are 75,000 smokers in Ealing, and it is hoped 7,500 will take the new test, with 2,400 going on to quit completely.

Forest spokesman Neil Rafferty said: ‘It shows the authorities think they have a blank cheque to treat smokers how they want – to harass, humiliate and victimise them.

‘This is an outrageous abuse of freedom and privacy. It is the health Nazi equivalent of chuggers.’